Variable-reluctance electrical generator

ABSTRACT

An electrical generator particularly designed to generate high voltages is disclosed. The generator includes an induction coil and a driven rotor associated with the coil and a curvilinear, spirally or helically-shaped band made of ferromagnetic material provided on the surface of the rotor. A magnet is provided which produces a magnetic field. The terminal sections of the ferromagnetic band which envelop a section of the induction coil are positioned opposite to the North and South poles of the magnet and the ferromagnetic band is so proportioned and affixed that the maximum effective band length for transmitting continuous magnetic flux to the induction coil, measured in degrees of angle, is 720*, and the minimum effective band length is 360*. The width of the poles and the gap between the poles are of such a dimension that when the ferromagnetic band turns through half a revolution the effective band length for the magnetic flux is changed by 360*.

United States Patent [191 Imris 1 1 VARIABLE-RELUCTANCE ELECTRICALGENERATOR [76] Inventor: Pavel lmris, Konigsbergerstr. 4,

Eldagsen, Germany [22] Filed: Sept. 11, 1972 21 Appl. No.: 287,821

- [30] Foreign Application Priority Data Nov. 12, 1971 Germany... P 2156 274.3

521 US. (31.... 310/168, 310/266 [51] Int. Cl. H02k 19/20 [58] Field ofSearch 310/111, 168, 266, 310/155, 261, 67,169,170, 163

[56] References Cited UNITED STATES PATENTS 2,221,812 11/1940 Nilson310/163 2,418,471 4/1947 Holden et a1. 310/111 2,796,542 6/1957 Bekey et31...... 310/168 X 3,132,269 5/1964 Craske 310/111 3,321,652 5/1967 Opel310/168 831,442 9/1906 Kelsey 310/168 3,071,703 1/1963 Mathews 310/111FOREIGN PATENTS OR APPLICATIONS 996,645 12/1951 France 310/178 PrimaryExaminer-D. F. Duggan Attorney-Kurt Kelman [57] ABSTRACT An electricalgenerator particularly designed to generate high voltages is disclosed.The generator includes an induction coil and a driven rotor associatedwith the coil and a-curvilinear, spirally or helically-shaped band madeof ferromagnetic material provided on the surface of the rotor. A magnetis provided which produces a magnetic field. The terminal sections ofthe ferromagnetic band which envelop a section of the induction coil arepositioned opposite to the North and South poles of the magnet and theferromagnetic band is so proportioned and affixed that the maximumeffective band length for transmitting continuous magnetic flux to theinduction coil, measured in degrees of angle, is 720, and the minimumeffective band length is 360. The width of the poles and the gap betweenthe poles are of such a dimension that when the ferromagnetic band'tumsthrough half a revolution the effective band length for the magneticflux is changed by 360.

7 Claims, 2 Drawing Figures VARIABLE-RELUCTANCE ELECTRICAL GENERATOR Theinvention relates to an electrical generator, and to a high-voltagegenerator particularly.

In modern industry, there is a heavy demand for high voltage powersupplies, for example in the chemical industry for chemical synthesis inelectrical discharges. At the present time high voltage power suppliesare, in practice, high voltage transformers connected with electricalgenerators, in which the resulting combination has a very highinductance. When, for example, a high voltage power supply of this kindis connected with an ozone generator, then the sparks persist for a longtime in the ozone generator and, because of this, the efficiency forproducing ozone is low.

In conventional rotary generators, vibrations occur in the rotor becauseof variations in the electrical current. These vibrations are hard tocontrol so that, in practice, it is a very difficult and expensivematter to ensure a constant speed of rotation in the rotor and thereby aconstant frequency in the current generated.

The object of the invention is the provision of an electrical generator,particularly for the generation of high voltages, which avoids theshortcomings set forth above.

This problem is solved in the generator according to the invention bythe fact that a ferromagnetic band envelops a section of the inductioncoil, and its terminal sections are located opposite the two poles of amagnet in such a manner that the effective band length transmittingmagnetic flux to the induction coil, varies cyclically during operationof the generator.

The curvilinear, spirally or helically-shaped band rotates between theelctro-magnet and a section of the induction coil, the coil itselfrunning inside the band parallel to the axis of the band and also aroundthe outer surface of the band.

Themagnet is located on the outer side of the band and the magneticfield extends from one pole piece by way of an air gap through theferromagnetic band and,

by way of another air gap, back to the other pole piece of the magnet.When the ferromagnetic band rotates around its axis the magnetic fluxflows longitudinally through the band alternatingly through 360 andthrough 2 X 360".

In this manner a high voltage is generated having a frequency directlyproportional to the speed of rotation of the band.

This frequency, because of the negligible effect of Lenzs force, can bekept within very precise bounds. For example, at 50 cycles, the accuracyof the frequency can be maintained between :t seconds", which is veryimportant for utilization of this generator in the field of plasmaphysics.

This generator, which needs no commutator, has a low inductance and forthat reason can be used wit special advantage in the following fields:

a. for the production of a so-called hybrid plasma under conditions ofarc discharge with very short sparks,

b. for the production of ozone by arc discharge,

0. for chemical synthesis,

d. for air purification in electro-static filters,

e. for the operation of so-called plasma generators in which, it ispossible to achieve practically a cos d) of one.

A generator according to the invention will now be described in moredetail withreference to the accompanying drawings in which:

FIG. 1 shows basic elements of the generator in side view; and

FIG. 2 illustrates the generator-in side elevation and partly insection.

During rotation of the ferromagnetic band 1 around its axis the magneticflux from the pole piece S to the pole piece N through the band, isnever interrupted. There is cyclic change in the effective band lengthcarrying the magnetic flux. If the length of the band 1 is measured indegrees of angle then the path of the magnetic flux varies during eachrevolution betweenl X 360, and 2 X 360.

When the band 1 rotates, the number of magnetized turns of the bandwhich act upon the induction coil 3 change cyclically between one andtwo. The effective length of the band can be any multiple of 360". Topro duce an ideal sine curve for the induced current the band 1 shouldhave n turns, wherein n is an integer and at least 2, and the poles ofthe magnet should be located at the beginning and at the end of the band1.

This means that whenever the band makes one revolution one sinusoidalcycle of electrical voltage is induced in the induction coil 3. Theinduction coil 3 and the electro-magnet 2 are stationary and only theferromagnetic, curvilinear, band 1 turns.

The frequency of the induced electrical voltage which depends on therotary speed of the ferromagnetic band and the voltage in the inductioncoil depends on the number of its windings as well as on the magneticflux and on the rotary speed of the band ll.

For high voltages the induction coil 3 is enclosed in a tubularcontainer 11 filled with transformer oil 13 or other insulating liquid,as is shown in FIG. 2.

The tube 11 is provided with bearings 10 which carry a coaxial supporttube 9 for the ferromagnetic band 1. The tube 9 is rotated by a motor(not illustrated) about the axis 4. The electro-magnet 2is energized bya coil 16 and carried by pedestals 17 on a platform on which thecontainer 11 is also fastened by means of supports 12. The container 11is made of metal, and, an insulation section 18 is provided in order toprevent an electrical current from also being induced in the container.

The pole pieces N, S of the electro-magnet 2, are made of a softferromagnetic material, and form a mag netic circuit with band 1. Whenthe band 1 rotates, an electro-motive force is induced in the inductioncoil 3 and varies with the applied magnetic flux in a sine cycle. If anelectrical resistance is inserted between the terminals 15 of the coilwhich project from the container 11 through insulating bushings 14, asinusoidally alternating electric current flows across the resistanceand through coil 3.

A very important advantage of this generator resides in the very lowinductance of the induction coil 3.

It is so low because the ferromagnetic band is always under theinfluence of the magnetic flux. The intensity of the magneticfield inband 1 is constant, whereby the relative magnetic inductivity of theband 1 is constant and small. The absolute magnetic inductivity of theband I should be as high as possible.

This low inductance is of advantage in the production of ozone as wellas for special applications in plasma chemistry and plasma physics. Thefrequency of the voltage produced by the generator, is stable ecause themechanical rotation of band 1 can be exactly regulated. The magneticflux which envelops the induction coil, in accordance with Lenz's Law,has an effect'on the rotation of the ferromagnetic band, which keeps therotor free of mechanical oscillations during rotation.

In the illustrated generator the length of the band must equal at leasttwice 360". For perfect sine curve shape of the electrical voltageproduced by this generator the following parameters may be utilized, byway of example only.

Length of the ferromagnetic band: 2-% X 360.

The axial width 6 of the band should be equal to the axial width of thegap between the turns of the-band l.

The gap 7 between the pole pieces S and N should be equal to the width 6multiplied by 4/3, while the width of each magnetic pole pieces shouldbe equal to the width 6 multipled by 5/3.

If, by way of example, the length of the band equals 3.666 X 360, thenthe gap 7 must be equal to:

(width 6 times 4/3) twice the width 6 of the band.

If the length of the band equals 4-% X 360, then the gap 7 must be equalto (width 6 of the band X 4/3) 4 times the width 6 of the band.

If the length of the band equals 5-2/3 X 360, then the gap 7 must beequal to (width 6 ofthe band x 4 3 6 times the width of the band,-and soon so that the gap 7 is equal to the width of the band times (2n 8/3), nbeing as defined above.

The ferromagnetic band 1 must be made of soft magnetic material, i.e.,the coercive force must be minimal, the hysteresis curve must be narrowand the magnetic permeability must be as high as possible. In addition,the electrical resistance of the ferromagnetic band must be as great aspossible. An ideal material for this band is ferrite, however, caststeel, permalloy or supertending about a section of said loop in aplurality of spaced turns transverse to said windings and passingthrough said opening;

'c. magnet means for inducing longitudinal magnetic flux in alongitudinal portion of said body constituting said turns; and

d. operating means for cyclically varying the length of said portion.

2. A generator as set forth in claim 1, wherein said turns define asurface of circular cross section about an axis, said magnet meansinclude two pole pieces, means for imparting opposite magnetic polarityto said pole pieces, mounting means mounting said pole pieces atrespective fixed radial distances relative to said axis from saidsurface, respective longitudinal portions of said body being nearestsaid two pole pieces, and said operating means include means for varyingthe axial spacing of said nearest portions from each other.

3. A generator as set forth in claim 2, wherein said mounting meansinclude means for holding said pole pieces in respective fixed axialpositions, and said means for varying said axial spacing include meansfor rotating said body about said axis.

4. A generator as set forth in claim 3, wherein said turns extend in acontinuous helix about said axis, said pole pieces are spaced from saidaxis in a common radial direction, and said operating means hold saidbody in a fixed axial position during said rotating.

5. A generator as set forth in claim 1, further comprising a containerenveloping said coil, and a body of liquid insulating material in saidcasing, said turns enveloping said container.

6. A generator as set forth in claim 5, wherein said operating meansinclude means for rotating said body about said section of said loop.

7. A geerator as set forth in claim 4, wherein said spaced turns extendin a helix about an axis, said body is a band having a longtudinallycontinuous face in a cylindrical surface about said axis, the number ofsaid turns is at least two, said magnet means including two pole pieces,means for imparting opposite magnetic polarity to said pole pieces,mounting means mounting said pole pieces in axially spaced axialalignment at respective fixed radial distances from said cylindricalsurface, said operating means including means for rotating said bodyabout said axis relative to said pole pieces and to said coil.

k i t i

1. An electric generator comprising: a. an induction coil having aplurality of windings and extending in a closed loop about an opening;b. an elongated body of ferromagnetic material extending about a sectionof said loop in a plurality of spaced turns transverse to said windingsand passing through said opening; c. magnet means for inducinglongitudinal magnetic flux in a longitudinal portion of said bodyconstituting said turns; and d. operating means for cyclically varyingthe length of said portion.
 2. A generator as set forth in claim 1,wherein said turns define a surface of circular cross section about anaxis, said magnet means include two pole pieces, means for impartingopposite magnetic polarity to said pole pieces, mounting means mountingsaid pole pieces at respective fixed radial distances relative to saidaxis from said surface, respective longitudinal portions of said bodybeing nearest said two pole pieces, and said operating means includemeans for varying the axial spacing of said nearest portions from eachother.
 3. A generator as set forth in claim 2, wherein said mountingmeans include means for holding said pole pieces in respective fixedaxial positions, and said means for varying said axial spacing includemeans for rotating said body about said axis.
 4. A generator as setforth in claim 3, wherein said turns extend in a continuous helix aboutsaid axis, said pole pieces are spaced from said axis in a common radialdirection, and said operating means hold said body in a fixed axialposition during said rotating.
 5. A generator as set forth in claim 1,further comprising a container enveloping said coil, and a body ofliquid insulating material in said casing, said turns enveloping saidcontainer.
 6. A generator as set forth in claim 5, wherein saidoperating means include means for rotating said body about said sectionof said loop.
 7. A geerator as set forth in claim 4, wherein said spacedturns extend in a helix about an axis, said body is a band having alongtudinally continuous face in a cylindrical surface about said axis,the number of said turns is at least two, said magnet means includingtwo pole pieces, means for imparting opposite magnetic polarity to saidpole pieces, mounting means mounting said pole pieces in axially spacedaxial alignment at respective fixed radial distances from saidcylindrical surface, said operating means including means for rotatingsaid body about said axis relative to said pole pieces and to said coil.